I just thought I would post this up as a refernce for anyone having problems on this motherboard when it comes to loading video card drivers.

On 2 occasions, with quite different setups, got the same problems.

System 1
AMD X2 7750 (clocked at 3.0GHz/core)
Kingston HyperX PC6400
Saphire 4850 x 2 Crossfire

System 2
AMD Phenom II 940
Corsair XMS2 PC6400
Zotac 9800GTX+

With both of these is that after loading Vista 64bit onto either (and had the same problem with test installs of XP and Vista 32bit) everything works fine. Load all motherboard drivers. All good. Install Video card drivers and when PC says it needs to restart for changes to take effect, PC restarts, POSTs, starts loading Vista (or XP) with the loading bar. and then black screen. When you restart the PC, Windows knows taht it wasn't shut down properly, so you know that Windows has continued to load.

Enter BIOS
Unlock gigabyte advanced user options (Ctrl + F1)
Enter Advanced Chipset Features
->PCI-E configuration (don't remember the exact menu)
--->Set PCI-E 16x slot from Auto to Software Switch

I'm not sire if this is a shift in the way things used to behave to a new way of doing things or if it is a glitch with the BIOS and is in need of a new BIOS revision to correct it.